Do you have a brown thumb?

FFAGENTS

April 05, 2013|By David Graper, Extension Horticulture Specialist

There are lots of people out there that really struggle to keep plants alive; they tend to kill them off in just a matter of a few weeks. You might hear them say that they just don't have a green thumb, or maybe they say they have a brown thumb. Actually if you find that your thumb is green or abnormally brown, you had better wash your hands or perhaps see a doctor! But seriously, there are some folks that just don't seem to have the knack of growing and caring for plants. And that's OK, they are probably great at doing other things and frankly, it's those folks that keep some of us in a job trying to figure out what they might be doing wrong. In many cases, what they are doing wrong probably relates to watering, especially when it comes to houseplants. Overwatering is the number one killer of houseplants and the same can be said for outdoor plants in many cases too.

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The first thing that people need to understand is that water is essential for plants to live. That means you have to water your plants. But they also need to understand that plants also need oxygen too. You might think that the need for oxygen is not a problem since there is so much oxygen in the air all around us. But it's the roots that are often the part of the plant that get starved for oxygen because they might be getting too much water from overwatering that there isn't room for any oxygen to get down to the roots in the potting soil. All the living cells in a plant need to have access to oxygen in order to survive and undergo respiration.

At this point you might say, wait a minute, I thought plants produce oxygen! Yes, that is true of the parts of the plant that are green and are exposed to light so that they can make oxygen through the process of photosynthesis. But, remember that the roots are usually not green and usually are not exposed to light. So, they have to get access to oxygen from the air in the pores in the soil around them. But, if those pores are filled with water most of the time, there is very little oxygen available to them. The result is often that cells and whole sections of the roots can die. As the roots die or get infected with some root rot disease, the plant is going to start wilting. And, of course, what do you do when a plant is wilted? You water it, which just makes the problem worse.

The key to proper watering practices revolves around watering plants at the proper time and with the right amount. The basic rule is do not water a plant until it needs it, but when you do water, water thoroughly. Thorough watering means that the root ball is totally saturated at each watering then allowed to dry out partially before watering again. In order to saturate the root ball, you have to apply enough water so that some of it, ideally about 20% of what is applied, runs out of the bottom of the pot. This means that you need to have your plant in a pot that has a drainage hole in the bottom. Some containers do not! So, you have to be extra careful with plants in those situations.

Generally the best thing to do is put the plant in a pot with drainage holes, then place that pot in your fancy container. Then you can either take the plant out of the container to water it or empty the container after watering. You will also probably need to have the plant on a pot saucer to catch the excess water, known as leachate. When sufficient water is applied to allow for some of it to run out the bottom of the pot that excess water helps to dissolve built-up fertilizer salts that may be in the potting soil and leach it out of the pot, which is very helpful in maintaining a healthy plant. Some plants are sensitive to excess salts in the potting soil which can lead to damage to roots and eventually damage to foliage.

After you have watered your plant and the leachate has drained out of the pot and into your saucer, you should then empty the saucer. Otherwise, the leachate accumulates in the saucer and is later reabsorbed by the plant. This means that even though excess salts were leached out during watering, those salts are mostly reabsorbed into the potting soil as the plant begins to dry out. Those excess salts are generally left as a brownish deposit on the top of the growing media, left there as water evaporates from the surface of the potting soil. Over time, those salts can accumulate on the rim of the pot and even cascade down the side of the pot. The excess salts are also unsightly and can lead to damage to your window sill, table or floors as well.

Another way to thoroughly water your plants and not make a mess is to take your plant and water it in a sink. This works great for smaller plants but not very well for larger plants that are just too heavy to move. Remember to keep adding water until you see water running out of the bottom of the pot. It certainly won't hurt your plant to just let the water run in a slow stream for 10 minutes or so, to thoroughly saturate the root ball and give it a good leaching too. You might think this would cause overwatering. But overwatering occurs when you keep the soil too wet for too long. You can't overwater a plant by applying too much water at one time, as long as you let the potting soil dry out somewhat before watering again.